public class animal {
    public static void main(String[] args) {
        //静态内部
        bird.dog d1 = new bird.dog();
        d1.eat();
        //
        bird b1 = new bird();
        bird.cat c1 = b1.new cat();
    }
}
class bird{
    static class dog{
        public void eat(){
            System.out.println("吃骨头");
        }
    }
    class cat{
        public void eat(){
            System.out.println("吃鱼");
        }
    }
}
